What does the internal bypass valve do in a Viessmann combi?

D

dr911t

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• Dec 12, 2021

• #1

Could someone please explain what is the function of the internal bypass valve in a Viessmann combi and how its settings MIN/MAX or malfunction somehow would affect operation of DHW and heating?
Thanks in advance.

 

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ShaunCorbs

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• Dec 12, 2021

• #2

When the boiler switches from hot water to heating the water moving has to go somewhere when the diverter switches over

 

D

dr911t

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• Dec 12, 2021

• #3

ShaunCorbs said:

When the boiler switches from hot water to heating the water moving has to go somewhere when the diverter switches over

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is the bypass value always in the same position? does it only function when the diverter is in motion between DHW and heating?

 

ShaunCorbs

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• Dec 12, 2021

• #4

It’s set to x pressure so when the diverter moves the system increases pressure and the bypass activates

 

D

dr911t

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• Dec 14, 2021

• #5

ShaunCorbs said:

It’s set to x pressure so when the diverter moves the system increases pressure and the bypass activates

Click to expand...

So it should always be set on "MIN" and boiler does the rest?

 

ShaunCorbs

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• Dec 14, 2021

• #6

Should be set so under normal operation it doesn’t open

 

M

MaxPower

• Nov 14, 2023

• #7

The MIN pressure seems to be around 140 mbar. But what ist the opening pressure in the MAX position? I cannot find this information anywhere.

 

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John.g

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• Nov 15, 2023

• #8

Vaillant have a internal bypass ( on the primary circuit) on all their system and combi boilers, it is factory set to 250mar but is adjustable from a minimum of 170mbar to a max of 350mbar, it provides the minimum flowrate required by the boiler at reduced flow demand and pump overrun after boiler shutdown, Viessmann setting may be similiar.